JP3015007B2 - Test socket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test socket for an integrated circuit package such as a ball grid array package, wherein the test socket comprises an upper housing and a lower housing located around a loading substrate. When, and a plurality of individual contact pins, the individual contact pins extends through the stacked substrate from the lower housing, an independent spring force of the test socket
A compliant element of the lower housing for applying to the solid contact pins is brought into contact with the integrated circuit package.

[0002]

BACKGROUND OF THE INVENTION Testing of integrated circuits contained within a ball grid array (BGA) package is performed by using what is commonly referred to in the art as a test socket.
Typically, a BGA test socket includes a housing mounted on a loading board that interfaces with test electronics. The mounting board is generally a circuit board for transmitting test signals from the BGA integrated circuit to the test electronics.

[0003]

Prior methods of attaching test sockets to a mounting substrate include through hole technology and surface mount technology. In a surface mount connection, the test socket is provided with a test pad, which contacts the solder ball at the bottom of the BGA when the BGA is pressed against the test pad to transmit a test signal to the mounting board. A problem associated with surface mount test socket placement is that the solder balls at the bottom of the BGA can vary in height so that effective electrical contact between each solder ball and test pad cannot always be guaranteed. . A second problem associated with surface mounting is that once the test pads become contaminated from the solder balls, the entire socket assembly must be replaced.

[0004] A through hole technique for connecting a test socket to a loading board includes a hole drilled in the loading board as a path for a spring-loaded contact pin, which contacts the BGA solder ball. In contact, a test signal is transmitted to the loading substrate by contact between the test pin and the hole in the loading substrate. A problem associated with the through-hole socket arrangement is that test pins extending upward through the loading board may be easily bent or damaged, which may negatively affect test results. To avoid this problem, a receptacle can be placed between the test socket and the loading board to protect the test pins extending through the loading board. As a result of incorporating the receptacle, it is necessary to increase the length of the test pins of the test socket, which creates problems with testing high speed integrated circuits. To address this problem, spring probes with short travel lengths have been used.
However , short travel springs have a short spring life and require constant replacement. Furthermore, the use of a spring probe in a test socket can create impedance problems with the transfer of test signals from the BGA to the loading board.

[0005] Therefore, there is a need for a new BGA package test socket that reduces the problems associated with prior art test sockets.

[0006]

SUMMARY OF THE INVENTION The present invention provides a newly designed test socket, and more particularly, a test socket for a ball grid array integrated circuit package, which reduces the problems associated with conventional test socket arrangements. Although in the preferred embodiment the test socket is designed for use with a BGA package, the test socket may be adapted for use with other integrated circuit packages, for example, a QFP package. Briefly, the test socket of the present invention comprises an upper housing and a lower housing fastened to a top surface and a bottom surface, respectively, of a loading substrate. The mounting board is a small circuit board that is electrically interfaced with the test electronics of the external tester. The upper housing has a cavity for receiving the BGA, and does not include multiple springs and receptacles.
A hole is provided in the lower surface to allow the body socket plunger to contact the solder ball at the bottom of the BGA. A solid socket plunger is disposed in the lower housing in a plurality of grooves formed in rows and columns, and further extends through a plurality of holes in rows and columns through the loading substrate and contacts the solder balls. An elastomeric diaphragm is disposed between the upper surface of the lower housing and the lower surface of the loading substrate, extends above the lower housing and extends below the plunger into a groove in the lower housing to raise the socket plunger upward. To provide a spring force biasing toward the BGA. The flexible diaphragm provides independent spring-loaded pressure contact to a movable socket plunger mounted on the lower housing. Alternatively and more preferably, a spring is located below the plunger of the lower housing to bias the plunger. A non-conductive ball is placed between the plunger and the spring to prevent interference during high frequency applications. Conductive tubular eyelets are positioned in the holes of the loading substrate to guide the travel of the socket plunger and to transmit test signals from the socket plunger to the loading substrate. Alternatively, the through holes in the loading substrate are plated for test signal transmission.

[0007] socket plunger of the present invention eliminates the problems associated with conventional BGA test socket arrangement by eliminating long lead length by using an individual socket plunger biased by elastomeric diaphragm Eliminates the problem of spring inductance. This arrangement further provides a long travel length for the plunger to compensate for the lack of coplanarity of the BGA solder balls. The use of an elastomeric diaphragm further increases the useful life of the test socket as compared to a mechanical spring.

[0008] Furthermore, the present test socket arrangement provides for easy and inexpensive retrofitting of test sockets by simple plunger replacement when contaminated by solder balls. The socket plunger is easily replaced by removing the lower housing and the resilient diaphragm, allowing the plunger to drop freely from the test socket. The refill cassette containing the new plunger is then placed on the lower surface of the loading substrate, and can then be turned over to reload the test socket with the new plunger. The resilient diaphragm and lower housing can then be reattached to the loading substrate for additional testing. This design allows retrofitting by simply replacing the plunger instead of the entire socket assembly. These and other advantages of the present invention will be more clearly understood with reference to the following detailed description.

[0009]

DETAILED DESCRIPTION OF THE INVENTION A test socket 10 for a ball grid array integrated circuit package 12 is shown in FIGS. Although the invention has been described and illustrated for use with a BGA package, the novel design of the present test socket is equally applicable to testing other integrated circuit packages. For clarity, most of the detailed description is limited to BGA packages. The test socket 10 of the present invention includes an upper housing 14 and a lower housing 16 that are fastened to a top surface 18 and a bottom surface 20, respectively, of a loading substrate 22. The upper housing 14 and the lower housing 16 are preferably made of plastic and are firmly attached to the loading substrate by screws 24 passing through the housing and into the loading substrate.
The mounting board is a circuit board that is electrically connected to a test electronic device of an external tester (not shown) by an interface.

The upper housing 14 includes a cavity 26 inside the upper housing 14 for receiving the ball grid array package 12. The ball grid array package includes an integrated circuit 28 disposed on a substrate 30 which is disposed on a lower surface of the substrate opposite the integrated circuit and is in electrical communication with the integrated circuit through the substrate 30. Having a plurality of solder balls 32. Solder ball 32
Serves as a test pad for testing integrated circuits. The substrate 30 rests on a flange 34 at the base of the cavity 26 and the solder balls 32
Extending into a hole 36 formed by the flange 34.

A hole 36 in the base of the upper housing further provides an opening to allow the plurality of solid socket plungers 38 to contact the solder balls 32. A socket plunger 38 is disposed in a plurality of grooves 40 formed in rows and columns in the lower housing 16 and, as best shown in FIG. 3, defines a plurality of through holes 41 through the loading board. Extending therethrough and contacting the solder balls 32. The through hole 41 is further provided with the solder ball 32 of the BGA package.
Are arranged in rows and columns in the same way as the pattern of The solid socket plunger 38 includes an enlarged head portion 42 and an elongated arm portion 44 having a smaller diameter. The arm portion extends through the hole 41 through the loading substrate 22 while the enlarged head portion 42 remains in the groove 40 of the lower housing 16.

An elastomeric diaphragm 46 is disposed between the upper surface 48 of the lower housing 16 and the lower surface 20 of the loading substrate, extends over the groove in the lower housing, and extends into the groove 40 in the lower housing 16. Extending downwardly, the beveled top surface 50 of the plunger arm portion 44 provides an electrically effective contact with the solder ball 32 by providing a spring force that biases the socket plunger 38 upwardly toward the BGA. Let them do it. The beveled surface 50 at the end of the plunger arm portion 44 is machined to provide a biased contact with the solder ball 32. Flexible diaphragm 4
6 provides independent spring-biased pressure contact to a movable socket plunger 38 mounted on the lower housing 16. In order to guide the travel of the socket plunger arm portion 44 and to transmit the generated test signal from the solder ball 32 through the socket plunger 38 to the loading board 22, the conductive cylindrical eyelets 52 are formed in the through holes of the loading board 22. 41. The eyelets 52 are preferably made from a conductive material such as copper beryllium or nickel silver. The through holes 41 of the loading substrate 22 are typically plated, and the eyelets 52 are
Soldering the eyelet 52 to the mounting substrate 22 to securely attach the eyelet 52 to the mounting substrate 22.
3 is provided.

An elastomer diaphragm 46 is held between the lower housing 16 and the loading substrate 22 by screws 24. The elastomeric diaphragm 46 is a thin flexible sheet, preferably made of inflatable latex rubber, which is a flexible, flexible sheet of socket plunger head 42.
Contact directly with. Although the preferred elastomeric diaphragm 46 is made from latex rubber, the use of other materials that cause the diaphragm 46 to provide a biasing spring force on the socket plunger is also contemplated. The diaphragm 46 in the normal position is extended and each plunger head 42
The axial force applied to each plunger in use in the direction of the diaphragm during use causes the diaphragm 46 to expand and conform to the end of the plunger in a manner similar to a typical return spring. To give. As the diaphragm 46 can freely expand or extend into the space of each groove 40, as the plunger moves axially, the thin flexible diaphragm 46 will
It can be freely expanded into. An axial force, in one embodiment as shown in FIG. 1, is hingedly connected to the upper housing 14 and fastened to the upper housing 14 in a closed position by a clasp (not shown). The lid 54 adds to the socket plunger 38. The housing lid 54 has an enlarged central portion 56 sized to push the BGA package down against the socket plunger 38 to extend the elastic diaphragm. Alternatively, an axial force can be applied to the BGA package by a robot arm 58 located on the BGA package and extending through the cavity 26 to the upper housing as shown in FIG. In this configuration, the housing lid is not required and is not held in the open position. The use of robotic arms may be incorporated into automated test configurations. The elastic diaphragm of FIG. 2 is shown in its normal position before an axial force is applied to the BGA package.

The test socket arrangement of the present invention provides a simple and inexpensive retrofit of the test socket 38 with the ability to easily replace the socket plunger 38 when the socket plunger 38 becomes contaminated by the solder balls 32. Through repeated use, the beveled surface 50 of the socket plunger 38 may become contaminated from tin or lead deposits from the solder balls. The repair can be easily performed by using the refill cassette 60 shown in FIG. The refill cassette 60 is preferably a plastic block including a plurality of recesses 62 formed in rows and columns and extending into the refill cassette for receiving a replacement socket plunger 64. FIG. 4 shows six replacement socket plungers 64 extending upwardly from recesses 62 for purposes of illustration. It will be appreciated that a separate socket plunger 64 is located within each recess 62 and is flush with the upper surface 66 of the refill cassette 60. The refill cassette further includes a positioning hole 68 to align the refill cassette 60 during the refurbishment process.

To refurbish the test socket, the contaminated socket plunger is easily removed by removing the lower housing 16 and the resilient diaphragm 46 to allow the contaminated plunger to drop freely from the test socket. Be exchanged. Next, the refill cassette 60 is placed over the lower surface 20 of the loading substrate 22 and is turned over to refill the test socket with a new plunger. The resilient diaphragm 46 and lower housing 16 are then reattached to the loading board 22 for another test.

Referring to FIG. 5, a first alternative test socket arrangement is shown. Test socket 70 of FIG.
Means that the lower housing 1
6 and 7 except that it is a spring 72 located in the groove 40 of FIG.
In this embodiment, upper surface 48 of lower housing 16 is adjacent to lower surface 20 of loading substrate 22. The groove 40 in the lower housing 16 is a dead end hole and does not extend through the lower housing 16 but terminates in a floor portion 74. This test socket is BGA
Although it can be used for packaging, FIG.
It shows that other integrated circuit packages having other types of test locations 76, such as test pads or leaders, can be tested.

A second alternative preferred test socket configuration 80 is shown in FIG. The test socket 80 is shown in FIGS.
And is substantially similar to the test socket of FIG. 5 and includes a different arrangement for biasing the plunger 82.
Hole 8 in which each plunger extends through lower housing 88
6 is urged by a spring 84 disposed in the housing 6. A spring 84 is retained in the hole 86 by a retaining cap 90 which is attached to a lower surface 92 of the lower housing 88 by screws (not shown). The retaining caps 90 cover the rows and columns of the holes 86 in the lower housing 88.

A ball 94 is located between plunger head 96 and spring 84. The ball 94 urges the plunger against the plated through hole or eyelet 98 of the loading substrate 100 by contacting the slope 102 at the bottom of the plunger head 96. To prevent interference with test signals, ball 94 may be a metal or a non-conductive material such as ceramic suitable for high frequency applications. The plunger further has a beveled end 104 for contacting the solder ball 106 of the integrated circuit 108. The bevel edge 104 ensures effective contact with the test location.

Although the present invention has been described and illustrated with respect to three embodiments, it will be understood that changes and modifications may be made within the full intended scope of the invention as set forth in the appended claims. It will be understood that this is not a limitation.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a BGA test socket of the present invention in a biased state.

FIG. 2 is a front sectional view of the test socket of FIG. 1 in a non-energized state.

FIG. 3 is an enlarged detail illustrating the socket plunger assembly.

FIG. 4 is a perspective view of a test socket refill cassette.

FIG. 5 is a front sectional view of another test socket arrangement.

FIG. 6 is a partial cross-sectional detail view of another configuration for biasing the plunger.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Test socket 14 ... Upper housing 16 ... Lower housing 22 ... Loading board 26 ... Cavity 28 ... Integrated circuit 30 ... Board 32 ... Solder ball 38 ... Individual socket plunger 40 ... Groove 46 ... Diaphragm 72 ... Spring 84 ... Spring

Continuation of front page (72) Inventor Charles Jay. Johnston United States of America, California 91789, Walnut, Los Gatos 411 (72) Inventor Gordon A. Binther United States of America, California 91107, Pasadena, South Roosevelt 103 (72) Inventor Steve Bee. Sargent United States, California, Los Alamitos, Lassen Street, 10322 Kaihei 6-61321 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 31/26 H01L 21/66 H01R 33/76

Claims (10)

(57) [Claims] 1. A test socket for an integrated circuit package having a plurality of test locations, said test socket being located on a circuit board.
And extends through for receiving the integrated circuit package
An upper housing having a cavity , positioned below the circuit board;
A lower housing having a plurality of grooves for receiving test pins placed therein, and the circuit board positioned below the circuit board;
The test pins that penetrate through the
A test socket for an integrated circuit package, comprising: a cage test location; and means having compliance for making electrical contact . 2. The circuit board having a plurality of holes, each hole guiding the travel of the test pins through the circuit board and transmitting a test signal from a test location of the integrated circuit package to the circuit board. The test socket for an integrated circuit package according to claim 1, further comprising a conductive eyelet. 3. The circuit board of claim 1, wherein the circuit board includes a plurality of plated through holes for guiding the travel of the test pins through the circuit board and transmitting test signals from the test location to the circuit board. Item 2. The test socket for an integrated circuit package according to Item 1. 4. The integrated circuit package test socket of claim 1, wherein said compliant means is a spring located in each groove of the lower housing below said test pin. 5. The test socket according to claim 4, further comprising a ball located between the spring and the test pin. 6. The test socket of claim 5 , wherein the ball is made of a non-conductive material. 7. The integrated circuit package test socket according to claim 5, wherein the test pin has a sloped end for contacting the ball. 8. A test fixture for an integrated circuit package having a plurality of test locations disposed on a lower surface of the package for an integrated circuit, the test fixture being located on a circuit board and receiving the integrated circuit package.
A top housing having a penetrating cavity extending for an upper housing in which the cavity extends to the opening for the test position of the base of the upper housing, positioned below the circuit board, respectively With test pin
A lower housing having a plurality of grooves provided therein, and a lower portion of the test pin in each groove of the lower housing.
At an axis for electrical contact with the test position
A test fixture for an integrated circuit package comprising: a spring for applying a directional force to the test pins . 9. The test fixture of claim 8, further comprising a ball located between each spring and each test pin of the groove. 10. The circuit board has a plurality of plated through holes for guiding travel of the test pins through the circuit board and for transmitting test signals from the integrated circuit package to the circuit board. 9. The method of claim 8, comprising:
A test fixture for an integrated circuit package according to claim 1.